In many applications, it is necessary to transfer particulate material from one location to another. For example, when applying particulate paint, commonly referred to as powder paint, in mass production applications, it is necessary to move the powder paint from a hopper in the powder paint storage room to the paint application area, wherein it is typically received in a feed hopper adjacent to the paint applicators.
In existing automotive powder paint application systems, the powder paint is transferred by a vacuum receiver system as disclosed, for example, in U.S. Pat. No. 5,743,958. As disclosed in more detail in U.S. Pat. No. 5,743,958, the powder paint transfer system includes a transport pipe, a receiver and a vacuum source which transfers the powder paint from a source, such as a storage hopper, to the application area. The receiver is a chamber or powder receiver coupled to a feed hopper. The vacuum source is connected to the receiver to withdraw air, substantially free from powder paint. The transport pipe is connected between the source of powder or particulate paint and the receiver to deliver a mixture of air and powder paint when the vacuum source is activated. The air/powder mixture enters the receiver and the powder paint is separated and collected, usually by a membrane filter. The air flows to the vacuum source and the collected powder is continuously or periodically discharged into the feed hopper. A gas-type sealing valve is required between the feed hopper and the receiver to avoid having gas flow from the feed hopper to the receiver. If the sealing valve is not included, this flow may impede the flow of powder paint from the receiver to the feed hopper or may prevent sufficient vacuum from being generated in the feed hopper to transport the powder from the source. There are several problems associated with the utilization of a vacuum to transfer particulate material, including powder paint, through a hose or line as disclosed in this patent. First, a vacuum is insufficient to transfer particulate material over long distances. The vacuum system disclosed in this patent is generally limited to about 100 feet. Further, the hose or line which conveys the powder paint must have a diameter of at least about two inches. Further, the powder paint is not conveyed in a dense phase and this system requires a receiver having a sealing valve, as described above.
Thus, it would be desirable to convey particulate material, particularly including powder paint, in a dense phase using a smaller delivery line over greater distances up to about 350 feet or greater. Further, it would be desirable to reduce the cost of the delivery system and eliminate the requirement for a receiver having a sealing valve system as described above. Reference is also made to U.S. Publication application 2001/0003568 A1 which discloses an apparatus for pneumatically conveying powder substances in a pipe system, wherein a volume is of powder is sucked in with reduced pressure and discharged with increased pressure. This apparatus includes a plurality of relatively small metering chambers (between 0.5 and 100 mm) and a metering pump which conveys the powder products in a metered continuously pulsating fashion. However, it is believed that the apparatus disclosed in this patent publication would not be suitable for powder paint and is relatively complex.
The pump for transferring particulate material of this invention is simple, yet rugged in construction and is particularly suitable for transferring powder paint which typically has a size range between 1 and 3 ∘ m or generally in the range of 15 to 25 μm. The powder pump of this invention further transports the particulate material in a dense phase, eliminating the requirement for a receiver having a filtration system as described above and may be utilized to transfer particulate material at least 350 feet or greater.